1. Field of the invention
This invention relates to a medium for electrophoresis, and more particularly relates to a medium for electrophoresis suitably employable for the determination of base sequence of DNA, RNA, their fragments, and their derivatives.
2. Description of prior art
For the determination of base sequence of DNA or RNA according to a chemical decomposition method and a dideoxy method, the slab electrophoresis using an aqueous polyacrylamide gel membrane (or medium) is necessarily employed. The aqueous polyacrylamide gel membrane employed for the above purpose is generally prepared by crosslinking polymerization of approx. 95 weight parts of a monomer such as acrylamide and approx. 5 weight parts of a two(or more)-functional crosslinking agent such as N,N'-methylenebisacrylamide in an aqueous solution (concentration: approx. 3 to 30 wt. %).
At the present time, it is desired to make a thinner gel membrane so as to enhance the resolving power for resolving nucleic acid fragments. However, if the conventionally employed polyacrylamide gel membrane is made thinner in its thickness, such gel membrane gives a distorted resolved pattern as illustrated schematically in FIG. 2. FIG. 2 shows that resolution bands 2, each 1 of the bands corresponding to nucleic acid fragments having high molecular weight excessively extend in the width direction with distortion of the band shape. Such distorted bands make it difficult to read the resolved pattern.
Japanese Patent Provisional Publication 60(1985)-60548, etc. disclose that glycerol can be incorporated into a gel membrane as a wetting agent in an amount of approx. 1 to 40 wt/v %. However, the incorporation of glycerol as a wetting agent is considered to require a relatively great amount because incorporation of glycerol in a small amount near to the above lower limit shows too low wetting effect. The incorporation of glycerol into the gel membrane in an excessively great amount is not favorable because such incorporation makes the membrane so soft and extensile as to decrease handling efficency.